1. Field of the Invention
The present invention relates to a linear actuator for reciprocally moving a slide table in axial directions of a cylinder body by introducing a fluid under pressure into a cylinder chamber in the cylinder body through fluid outlet/inlet ports.
2. Description of the Related Art
Linear actuators have heretofore been used as means for conveying workpieces or the like. Linear actuators are capable of linearly reciprocally moving a movable table along a cylinder body for thereby conveying a workpiece placed on the movable table.
One known linear actuator is disclosed in Japanese laid-open utility model publication No. 5-42716, for example. FIGS. 6A and 6B of the accompanying drawings illustrate the disclosed linear actuator in the form of a fluid pressure cylinder assembly. As shown in FIGS. 6A and 6B, the fluid pressure cylinder assembly, generally designated by the reference numeral 1, comprises a cylinder body 2, a guide rail 3 projecting upwardly from and extending longitudinally on an upper surface of the cylinder body 2, and a slide table 4 mounted on the guide rail 3 for sliding displacement therealong in response to displacement of a piston disposed in a cylinder chamber which is defined in the cylinder body 2.
The slide table 4 has a ball circulation hole (not shown) defined longitudinally therein and accommodating a plurality of balls for rolling movement therein. The slide table 4 also has a plurality of screw holes 5a.about.5d that are defined in an upper surface thereof for attachment of a workpiece to be conveyed by the fluid pressure cylinder assembly 1. The cylinder body 2 has a pair of attachment holes 6a, 6b defined in respective diagonally opposite corners thereof for installing the cylinder body 2 on another member (not shown).
The cylinder body 2 has a transverse width L represented by L.apprxeq.L.sub.1 +(L.sub.2 .times.2) where L.sub.1 is the width of the guide rail 3 and L.sub.2 is the diameter of each of the attachment holes 6a, 6b. Therefore, the transverse width L is substantially equal to the sum of the width L.sub.1 of the guide rail 3 and the diameters L.sub.2 of the attachment holes 6a, 6b. The width L.sub.1 of the guide rail 3 cannot be reduced because the rigidity of the slide table 4 would be lowered if width L.sub.1 were reduced. As a result, the transverse width L is required to be substantially equal to the sum of the width L.sub.1 of the guide rail 3 and the diameters L.sub.2 of the attachment holes 6a, 6b so that the cylinder body 2 maintains a desired level of rigidity.
Inasmuch as the transverse width L of the cylinder body 2 cannot be reduced because of the required width L.sub.1 of the guide rail 3, the fluid pressure cylinder assembly 1 cannot be reduced in size and weight.
A process of machining a slide table blank into the slide table 4 is complex because the ball circulation hole needs to be defined longitudinally in the slide table blank and the screw holes 5a.about.5d need to be defined in the slide table in a direction different from the direction of the ball circuit hole.